As more and more states legalize the use of marijuana for medical and recreational use, the Surgeon General has stepped in with an important warning, saying that no amount of the drug is safe for teens, young adults, and pregnant women.

“While the perceived harm of marijuana is decreasing, the scary truth is that the actual potential for harm is increasing,” Surgeon General Jerome Adams said Thursday during a press conference to announce the new advisory.

More and more teens and pregnant women are using the drug, which can be smoked, vaped or eaten, but — and here’s a startling fact– the THC in today’s marijuana plants has increased.

“This ain’t your mother’s marijuana,” he said. The THC concentration in marijuana plants has increased threefold between 1995 and 2014, according to the report, and concentrated products can contain up to 75% THC.

An earlier study showed that even smoking pot a few times can change the teen brain, which is still developing and yet another experiment found that teen brains are more vulnerable to the effects of alcohol than cannabis.

At the University of Pennsylvania, scientists discovered that young people who used marijuana frequently were ‘more likely than nonusers to have slightly lower scores on tests of memory, learning new information, and higher-level problem solving and information processing.’

So if you are pregnant or an adolescent, just take a pass on that joint.